Parent-of-origin testing for 15q11-q13 gains by quantitative DNA methylation analysis.

The Prader-Willi/Angelman syndrome critical region (PWS/ASCR), located at chromosome 15q11-q13, is associated with several diseases. Absence of paternally expressed genes in this region cause Prader-Willi syndrome (PWS), whereas absence of the maternally expressed UBE3A gene causes Angelman syndrome (AS). In addition, duplications and triplications of this region are also associated with distinct clinical features, indicating that the overexpression of genes within the PWS/ASCR can also lead to distinct phenotypes.